Addressable switch assembly for wellbore systems and method

ABSTRACT

A method for controlling a target switch assembly in a chain of switch assemblies includes distributing the chain of switch assemblies in a wellbore; placing a controller at a head of the wellbore; making a first decision, at the controller, to actuate a corresponding detonator of the target switch assembly; transmitting, from the controller to the target switch assembly, a fire command to activate the corresponding detonator; and making a second decision, locally, at the target switch assembly, to activate the detonator, after the fire command from the controller is received.

BACKGROUND Technical Field

Embodiments of the subject matter disclosed herein generally relate todownhole tools for perforating operations, and more specifically, to agun string having one or more addressable switch assemblies forselectively activating a detonator from a plurality of detonators.

Discussion of the Background

After a well 100 is drilled to a desired depth H relative to the surface110, as illustrated in FIG. 1, and the casing 110 protecting thewellbore 104 has been installed and cemented in place, it is time toconnect the wellbore 104 to the subterranean formation 106 to extractthe oil and/or gas.

The process of connecting the wellbore to the subterranean formation mayinclude the following steps: (1) placing a plug 112 with a through port114 (known as a frac plug) above a just stimulated stage 116, and (2)perforating a new stage 118 above the plug 112. The step of perforatingis achieved with a gun string 120 that is lowered into the well with awireline 122. A controller 124 located at the surface controls thewireline 122 and also sends various commands along the wireline toactuate one or more gun assemblies of the gun string.

A traditional gun string 120 includes plural carriers 126 connected toeach other by corresponding subs 128, as illustrated in FIG. 1. Each sub128 includes a detonator 130 and a corresponding switch 132. Thedetonator 130 is not connected to the through line (a wire that extendsfrom the surface to the last gun and transmits the actuation command tothe charges of the gun) until the corresponding switch 132 is actuated.The corresponding switch 132 is actuated by the detonation of adownstream gun. When this happens, the detonator 130 becomes connectedto the through line, and when a command from the surface actuates thedetonator 130, the upstream gun is actuated.

For a conventional perforating gun string 120, carriers 126 are firstloaded with charges and a detonator cord. Gun strings are then built up,one gun assembly at a time, by connecting the loaded carriers 126 tocorresponding subs 128. These subs contain the switch 132 with pressurebulkhead capabilities. Once the sub is assembled to the gun string, thewires and detonation cord are pulled through the port in the sub,allowing for the installation of the detonator, the correspondingswitch, and the connection of the wirings. Those skilled in the fieldknow that this assembly operation has its own risks, i.e., miswiring,which may render one or more of the switches and correspondingdetonators unusable.

After a conventional gun string has been assembled, none of thedetonators are electrically connected to the through wire or throughline running through the gun string. This is because between each gunassembly there is a pressure-actuated single pole double throw (SPDT)switch. The normally closed contact on these switches connects thethrough wire from gun assembly to gun assembly. Once the switch has beenactivated by the blast of the gun assembly beneath (when that guns goesoff), the switch changes its state, connecting the through wire comingfrom above to one lead of the detonator. The other lead of the detonatoris wired to ground the entire time.

In this configuration, after assembly, it is not possible to selectwhich switch of the plurality of switches is to be activated. Once afire command is sent from the controller 124, the most distal switch isactivated. The blast from the corresponding gun assembly then activatesthe next switch and so on.

U.S. Pat. No. 6,604,584 discloses a downhole activation system that usescontrol units having “pre-assigned identifiers to uniquely identify eachof the control units,” and based on these identifiers, a centralcontroller can communicate with a selected control unit. This downholeactivation system requires the central controller to interrogate, whenthe system is started, each control unit to determine its address. If anaddress has not been assigned to a control unit, the downhole activationsystem would assign an address to that control unit. However, thisprocess is cumbersome and slow.

In addition, the system of U.S. Pat. No. 6,604,584 does not address howthe setting tool is activated. In this regard, note that the settingtool has its own detonator and switch. Previously, the setting toolrequired a separate and unique addressable switch for its actuation,which further complicates the firing of the detonators.

Thus, there is a need to provide a downhole system that overcomes theabove noted problems and offers the operator of the system thecapability to select any of the switches present in the gun string to beable to fire a desired gun assembly and/or the setting tool.

SUMMARY

According to an embodiment, there is a method for controlling a targetswitch assembly in a chain of switch assemblies. The method includesdistributing the chain of switch assemblies in a wellbore, placing acontroller at a head of the wellbore, making a first decision, at thecontroller, to actuate a corresponding detonator of the target switchassembly, transmitting, from the controller to the target switchassembly, a fire command to activate the corresponding detonator, andmaking a second decision, locally, at the target switch assembly, toactivate the detonator, after the fire command from the controller isreceived.

According to another embodiment, there is a switch assembly, which ispart of a chain of switch assemblies, the switch assembly including acommunication unit (CU) configured to receive, from an externalcontroller, a fire command to activate a detonator and a computing core(CC) configured to locally make a decision to activate the detonator,based on (i) a measured parameter (V), (ii) a threshold value of themeasured parameter (V), and (iii) the fire command.

According to yet another embodiment, there is a downhole system thatincludes a controller located at the surface, a gun string located in awellbore, the gun string including plural gun assemblies, a thru-lineconnecting the controller to the gun string, and a detonator blockattached to a given gun assembly. The detonator block includes anaddressable switch assembly.

According to still another embodiment, there is a method for selectivelyfiring a setting tool detonator and a gun assembly detonator. The methodincludes connecting an addressable switch assembly to the setting tooldetonator and to the gun assembly detonator, placing the addressableswitch assembly, the setting tool detonator, and the gun assemblydetonator inside a wellbore, receiving a command at the addressableswitch assembly, from a surface controller, wherein the command includesa digital address and an indicator, and firing the gun assemblydetonator if the indicator has a first value and firing the setting tooldetonator if the indicator has a second value, different from the firstvalue.

According to another embodiment, there is a switch assembly, which ispart of a chain of switch assemblies. The switch assembly includes acommunication unit (CU) configured to receive, from an externalcontroller, a command to activate a gun assembly detonator or a settingtool detonator and a computing core (CC) configured to locally make adecision to activate one of the gun assembly detonator or the settingtool detonator, based on (i) a measured parameter (V), (ii) a thresholdvalue of the measured parameter (V), and (iii) the received command.

According to yet another embodiment, there is a downhole system thatincludes a controller located at the surface, a gun string located in awellbore, the gun string including plural gun assemblies and a settingtool, a thru-line connecting the controller to the gun string, and atleast an addressable switch assembly configured to actuate a gunassembly detonator and a setting tool detonator.

BRIEF DESCRIPTION OF THE DRAWINGS

The accompanying drawings, which are incorporated in and constitute apart of the specification, illustrate one or more embodiments and,together with the description, explain these embodiments. In thedrawings:

FIG. 1 illustrates a well and associated equipment for well completionoperations;

FIG. 2 illustrates a chain of addressable switch assemblies andassociated gun assemblies;

FIGS. 3A and 3B illustrate possible configurations of an addressableswitch assembly;

FIG. 4 is a flowchart of a method for selecting an addressable switchassembly and actuating an associated detonator;

FIG. 5 illustrates a configuration of a frame that is associated with acommand;

FIG. 6 illustrates a gun string having a detonator block;

FIG. 7 illustrates an inside of the detonator block;

FIG. 8 illustrates a contact end plate mechanism;

FIG. 9 illustrates various components of the contact end platemechanism;

FIG. 10 illustrates a sub connected to a gun assembly through adetonator block;

FIG. 11 is a flowchart of a method for actuating a gun detonator; and

FIG. 12 is another flowchart of a method for actuating a gun assemblydetonator and a setting tool detonator.

DETAILED DESCRIPTION

The following description of the embodiments refers to the accompanyingdrawings. The same reference numbers in different drawings identify thesame or similar elements. The following detailed description does notlimit the invention. Instead, the scope of the invention is defined bythe appended claims. The following embodiments are discussed, forsimplicity, with regard to switch assemblies located insidecorresponding subs and the switch assemblies have plural switchesimplemented in software. However, the embodiments discussed herein arealso applicable when the switch assemblies having plural switches areimplemented in hardware and/or when the switch assemblies are located inanother component of the gun string than the sub.

Reference throughout the specification to “one embodiment” or “anembodiment” means that a particular feature, structure or characteristicdescribed in connection with an embodiment is included in at least oneembodiment of the subject matter disclosed. Thus, the appearance of thephrases “in one embodiment” or “in an embodiment” in various placesthroughout the specification is not necessarily referring to the sameembodiment. Further, the particular features, structures orcharacteristics may be combined in any suitable manner in one or moreembodiments.

According to an embodiment illustrated in FIG. 2, a gun string 200includes plural gun assemblies 240 (shown as elements 240A to 240M,where M can take any numerical value) connected to each other throughcorresponding subs 210 (numbered 210A to 210M in the figure). Note thateach gun assembly (except for the upper gun assembly 240A and the lowergun assembly 240M) is sandwiched by two subs. The upper gun assembly240A is considered to be the gun assembly first connected to thewireline (not shown in FIG. 2) and the lower gun assembly is consideredto be the gun most distal from the wireline, i.e., the gun assembly thatis connected to the tool setting 202.

Plural switch assemblies 232A to 232M and plural detonators 230A to 230Mare distributed along the gun string 200. In this embodiment, each sub210 includes a corresponding switch assembly and a detonator, i.e., sub210A includes switch assembly 232A and detonator 230A. The same is truefor all other subs. Note that it is possible to have a gun string thathas no sub. In this case, the switch assembly and the detonator arelocated in corresponding gun assemblies 240A. Detonator 230A iselectrically connected to switch assembly 232A and ballisticallyconnected the corresponding gun assembly 240A. The same is true for theother gun assemblies, detonators and switch assemblies.

The switch assembly 232A (in the following, reference is made to aparticular switch assembly, but it should be understood that thisdescription is valid for any switch assembly in the chain of switchassemblies shown in FIG. 2) includes a processor P_(A) (e.g.,application-specific integrated circuit or field-programmable gate arrayor equivalent semiconductor device) that is electrically connected totwo switches. A first switch is the thru-line switch 234A, which may beimplemented in software, e.g., firmware, or hardware or a combination ofboth. The thru-line switch 234A is connected to a thru-line 204. Thethru-line switch 234A is controlled in this embodiment by the processorP_(A). The thru-line 204 may extend from a surface controller 206 alongthe wireline. The portion of the thru-line 204 that enters the switchassembly 232A is called herein the input thru-line 204A-i and theportion that leaves the switch assembly 232A is called the outputthru-line 204A-o. When the thru-line switch 234A is open, power or othersignals send from the controller 206 cannot pass through the switchassembly 232A, to the next switch assembly 232B. By default, all thethru-line switches 234A to 234M are open.

In this embodiment, controller 206 can send not only commands, but canapply various voltages to the thru-line 204. This embodiment shows onlya single line (the thru-line 204) extending from the controller 206 tothe lower thru-line switch 234M. However, those skilled in the art wouldunderstand that more than one wire may extend from the controller 206 tothe various switch assemblies. For example, a ground wire may extend inparallel to the thru-line. In this embodiment, the ground wire's role isperformed by the casing of the gun assembly.

The switch assembly 232A also includes a detonator switch 236A, which isalso controlled by processor P_(A). The detonator switch 236A may beimplemented similar to the thru-line switch 234A. The detonator switch236A is by default open, and thus, no controlling signal is transmittedfrom the controller 206 or the processor P_(A) to the correspondingdetonator 230A. The switch assembly 232A may also include a memory 238A(e.g., EPROM memory) for storing a digital address.

The digital address of a switch assembly may be assigned in variousways. For example, it is possible that all the switch assemblies have apre-assigned address. In one application, it is possible that the switchassemblies have random addresses, i.e., addresses either assigned by themanufacturer of the memory or addresses that happen to be while thememories were manufactured. In still another embodiment, it is possiblethat a set of predetermined addresses were assigned by the manufacturerof the gun string.

The lower switch assembly 234M is different from the other switchassemblies in the sense that the switch assembly 234M is also connected,in addition to the input thru-line 204M-i and to the detonator 230M, toa setting tool detonator 250. The setting tool detonator 250 may havethe same configuration as the detonator 230M, but it is used to actuatethe setting tool 202. The setting tool 202 is used to set the plug 112(see FIG. 1). Thus, the lower switch assembly needs to distinguishbetween two modes: (1) firing the gun detonator 230M or (2) firing thesetting tool 202. A method for achieving these results is discussedlater.

A configuration of a switch assembly 232 (which can be any of the switchassemblies 232A to 232M discussed with regard to FIG. 2) is illustratedin more detail in FIGS. 3A and 3B. Switch assembly 232 includes thethru-line switch 234 and the detonator switch 236. As discussed above,these two switches may be implemented in hardware (e.g., withsemiconductor devices that may include one or more diodes and/ortransistors) or in software or both. In this embodiment, it is assumedthat the two switches are implemented in software (i.e., in theprocessor P_(A)). In this case, the two switches 234 and 236 in FIGS. 3Aand 3B are logical blocks that describe the functionality performed bythese switches and also their connections to other elements. This meansthat these logical blocks are physically implemented in processor P_(A).

Processor P_(A) may also include a logical voltage measuring block V_(M)that is configured to measure a voltage present in the thru-line 204, ormore specifically, the input thru-line 204-i. Further, the processor mayinclude a logical block I/O that exchanges various input and outputcommands with the controller 206 through the thru-line 204. Logicalblock I/O may also communicate with the voltage measuring block V_(M)for receiving the measured voltage V and providing this value to thecomputing core CC of the processor for performing various calculations.Processor P_(A) is connected to the memory 238 via a bus 239. Computingcore CC is capable of storing and/or retrieving various data from thememory 238 and performing various calculations. In one embodiment,memory 238 is an erasable programmable read-only memory (EPROM), whichis a type of memory chip that retains its data when its power supply isswitched off. This type of memory has the advantage of retaining anaddress associated with the switch assembly when no power is supplied.Regarding power, it is noted that in this embodiment the switch assemblyreceives its power along the thru-line 204, i.e., there is no localpower supply in the switch assembly or the sub.

The processor P_(A) may further include a communication unit CU that isconfigured to exchange data with the controller 206. As will bediscussed later, various commands are sent by the controller 206 to agiven switch assembly. The communication unit CU intercepts thosecommands (which are sent along the thru-line 204) and determines, incollaboration with the computing core CC whether the commands areaddressed to the specific switch assemblies. The communication unit CUis also configured to send an address (the digital address of the switchassembly, which is stored in the memory 238) of the switch assembly tothe controller 206 upon a powering operation of the switch assembly. Thecommunication unit CU may be configured to use any known communicationprotocol. The communication unit CU may be implemented in software, as alogical block in the processor P_(A), as illustrated in FIG. 3A.However, the communication unit may also be implemented as dedicatedhardware or a combination of hardware and software. For example, FIG. 3Bshows the communication unit CU being implemented as a receiver R and atransmitter T. FIG. 206 also shows a local controller 206′.

The processor P_(A) may further include one or more timers. FIG. 3Ashows a first timer 246A and a second timer 246B. These timers may beimplemented in software, and thus the blocks labeled 246A and 246B inFIG. 3A describe logical blocks associated with these timers. Thesetimers may be implemented in controller 206′ in the embodimentillustrated in FIG. 3B. However, in one embodiment, these timers may beimplemented as dedicated hardware in combination or not with appropriatesoftware. Although FIG. 3A shows two timers, one skilled in the artwould understand from this description that only one timer may be usedor more than two timers. The timers are configured to count a given timeinterval. For example, the first timer 246A may count down from 20 swhile the second timer 246B may count down from 1 s. Other values may beused. Once the given time intervals have lapsed, the timers send amessage to the processor indicating this fact. As will be discussedlater, these timers may be used for implementing safety proceduresregarding the firing of a detonator.

FIG. 3A further shows two wires (fire wires) 236A and 236B beingconnected to the detonator switch 236. The embodiment of FIG. 3B usesonly a single wire 236A for connecting the detonator switch 236 to thedetonator 230. These two wires in FIG. 3A are connected to the detonator230, which is not part of the switch assembly 232. However, one skilledin the art would understand that the detonator may be made part of theswitch assembly. The elements discussed above with regard to the switchassembly 232 are located inside of a housing 242. The housing can bemade of a metal, e.g., aluminum, or a composite material. In oneembodiment that is discussed later, the switch assembly is locatedinside a detonator block, which is configured to also host thedetonator. The entire switch assembly may be distributed on a printedcircuit board 244, as schematically illustrated in FIG. 3A. Theembodiment of FIG. 3B shows that two lines 204 and 204′ are entering theswitch assembly, where one line has a positive voltage and the otherline has a negative voltage. The switch assembly may have a power supply205 that supplies a DC voltage (e.g., 5 V) to the controller 206′. Theembodiment shown in FIG. 3B also includes a failsafe mechanism 233 forthe thru-line switch 234 and a failsafe mechanism 235 for the detonatorswitch 236. A switch load detect unit 207 detects whether one of theswitches 234 or 236 has failed. If the answer is yes, the switch loaddetect unit 207 reports this issue to the controller 206′, whichinstructs the corresponding failsafe mechanism 233 or 235 to respond toa pressure change in the well to open or close the corresponding switch.

The structure shown in FIG. 3A or 3B can be used for all the switchassemblies illustrated in FIG. 2, i.e., for the switch assemblies thatare connected to a single detonator, but also for the lower switchassembly, which is connected to the gun detonator and the detonator ofthe setting tool. Previously, the setting tool required a separate andunique addressable switch for the actuation of the setting tooldetonator. The switch assembly illustrated in FIGS. 3A and 3B eliminatesthe need for the setting tool switch, as the bottom gun addressableswitch assembly's address allows that switch assembly to perform bothfunctions of applying a shooting voltage to the detonator of the settingtool and afterwards, applying the same or a different shooting voltageto the detonator of the bottom gun.

The digital addressable switch assembly of FIG. 3A or 3B is programmedto communicate with a surface logging and/or perforating system (e.g.,controller 206), which provides improved safety and perforatingreliability of individual gun control from the surface. Theconfiguration shown in FIG. 2, which includes plural addressable switchassemblies, has the ability of firing a single gun assembly, generallystarting at the bottom of the gun string. It also provides for skippingany one or more gun assembly in the gun string that may be defective,thereby continuing the perforating process of firing single gunassemblies with any of the remaining gun assemblies in a string.

The switch assembly 232 may be designed to provide an exact formreplacement to the EB style switches currently in use. The electroniccircuit board 244 of the switch assembly 232 may be potted within themetallic housing 242 by a thermally conductive, electrically isolationepoxy that also provides both electrical and mechanical shocksurvivability. The construction of the switch assembly has no movingparts, making it ruggedly built to withstand the blast of theperforating gun assembly and the downhole well pressure.

In one embodiment, each switch assembly's processor and/or memory ispre-programmed with a unique digital address, which is dynamicallycapable of being changed in the field. Each switch assembly ispositioned within a sub connected to a gun assembly to enable the firingof that specific gun assembly while maintaining pressure containment toenable the intrinsically safe arming, and shooting of a single specificgun assembly. A gun string, as discussed above, then consists ofmultiple pre-assembled and tested gun assemblies typically connected,end to end and lowered to the bottom of the production well. However, asdiscussed above, if no subs are used in a certain gun string, then theswitch assemblies are positioned in other parts of the gun string.

The gun string is shot starting with the setting tool, which sets adrillable bridge plug. Before the perforation operation begins, the plugseal is hydraulically tested and afterwards the bottom gun assembly inthe string is shot, followed by multiple gun assemblies being shot atpre-determined points along the course of the well bore. As each gunassembly is shot, the thru-line and electronics associated with thecorresponding addressable switch assembly is destroyed by the pressurewaves generated by the charges of the gun assembly. Therefore, theaddressable switch assembly cannot be re-used for a second shooting.However, the mechanical housing 242 of the switch assembly 232 isconfigured to maintain the pressure integrity of the adjoining gunassembly and the electronic circuitry is reset to prevent voltage beingapplied to accidentally fire a next gun assembly.

Each switch assembly may be configured in software internal to theprocessor P_(A) to provide the capability of firing a single gunassembly or, at the operator discretion, in the field, to be used as thebottom gun/setting tool switch. The lower switch assembly's firecapability is selected at the final assembly of the gun string bychanging the address, for example, to a pre-determined value to enablethat functionality.

The selection of a given switch assembly and various operationsassociated with the shooting of a gun assembly are now discussed withregard to FIG. 4. Suppose that the switch assemblies have been providedin the corresponding subs, and the subs have been connected to thecorresponding gun assemblies so that the entire gun string is assembled.Either before the gun string is lowered into the well, or after the gunstring has been deployed inside the well, power is applied in step 400from the controller 206 (see FIG. 2) through the wireline (that includesthe thru-line) to the gun string. At this time, as illustrated in FIG.2, all the thru-line switches of the switch assemblies are open, whichmeans that the power is received only by the upper switch assembly 232A,but not by the other switch assemblies.

Upon receiving power in step 400, the first switch assembly 232A sendsin step 402 its digital address to the controller 206. This digitaladdress, as discussed above, can be pre-assigned by the operator of thegun string before assembling the gun string, can be pre-assigned by themanufacturer of the gun string, or can be a random address that wasgenerated when the memory 238 was manufactured. In one embodiment, thedigital address can even be an incomplete address. After sending itsaddress, the switch assembly waits in step 404 for a command from thecontroller 206.

Controller 206, upon receiving the digital address of the first switchassembly of the chain of switch assemblies, stores this address in anassociated memory and maps the first switch assembly of the chain withthis digital address. This mapping may be recorded in a table kept bythe controller. The table would also include the digital addresses ofall the switch assemblies in the chain, as each switch assembly ispowered up.

After all the thru-line switches are closed and the controller is ableto communicate with each of them, further commands are sent from thecontroller. When a command from the controller 206 is sent along thethru-line 204, each switch assembly intercepts that command and verifiesin step 408 weather an address carried by the command matches theaddress of the switch assembly. If the result of this step is NO, theprocess advances to step 410, which returns the process to the step 406of waiting for a command. However, if the result of step 408 is YES,i.e., the command sent by the controller 206 is intended for the givenswitch assembly, the process advances to step 412, where a determinationis made of whether the command is valid for the given switch assembly.For example, suppose that the command includes the correct digitaladdress of the upper switch assembly 232A, but instructs it to fire thedetonator of the setting tool. As previously discussed, the setting toolis controlled by the lower switch assembly 232M, not the upper switchassembly 232A. In this case, step 412 determines that the command,although addressed to the correct switch assembly 232A, it not valid forthis switch assembly. Thus, the process is returned to step 406 forwaiting for another command.

However, if the received command has the right digital address and is avalid command for the switch assembly 232A, then the process advances tostep 414. In step 414, the processor of the switch assembly determineswhether the command is related to changing an address of the switchassembly. If the result of this determination is yes, then the processadvances to step 416 during which the original digital address of theswitch assembly is replaced with a new one selected by the operator ofthe chain. In other words, according to this step, the operatordynamically assigns new addresses to the switch assemblies of the chain.If a new address has been assigned in step 416, the new address iswritten to the memory 238 and then the process returns via step 410 tothe waiting step 406. Alternatively, if the original address of theswitch assembly is incomplete, using the process described above, theoperator is able to complete the address.

If the command from the controller 206 is not related to assigning a newdigital address, the processor P_(A) checks in step 418 whether thecommand is related to a “pass” command. A pass command is designed toclose the thru-line switch 234A so that power can be supplied to thenext switch assembly 2326. If this is the case, then in step 420 theprocessor P_(A) closes the switch 234A and the process returns to thewaiting step 406.

If the command received in step 418 is not a pass command, then theprocess advances to step 422, where it is determined whether the commandsend by the controller 206 is a “fire” command. A fire command instructsthe switch assembly to close the detonator switch for firing thecorresponding detonator. If the command in step 422 is a fire command,then the process advances to step 424, at which point the first timer246A is started. The first timer 246A may be programmed to count down afirst time interval, e.g., a 20 s period. Other time periods may beused. The processor checks in step 426 whether the time period haselapsed. If the answer is yes, then the process stops in step 428 thefirst timer (and other timers if they have been started) and returns tothe waiting step 406.

A second timer 246B may also be started in step 424. Starting thissecond timer is optional. If this second timer is present and started,then it counts down a second time interval, shorter than the first timeinterval of the first timer. In one application, the second timeinterval is about 1 s. When the processor determines in step 430 thatthe second time interval has lapsed, the processor sends in step 432 thestatus of the switch assembly (e.g., whether the switches are closed oropen, whether a voltage has been measured, etc.) back to the controller206. Further, in the same step 432, the second timer is reset to countdown again the second time interval.

The purpose of these two counters is now explained. Returning to step422, assume that a fire command has been send from the controller 206 tothe switch assembly 232A. To actually fire the detonator associated withthis switch assembly, it is not enough to only send the fire command(first condition) because that command may be send in error. Thus, asecond condition needs to happen in order to actuate the detonator. Thissecond condition is the detection in step 434 of a parameter (e.g.,voltage) characterizing the thru-line 204 and determining whether avalue of this parameter is larger than a given threshold. For example,the threshold voltage can be 140 V. Other values may be used. Note thata voltage in the thru-line during normal operation is much less than thethreshold voltage, e.g., about 30 to 40 V. Those skilled in the artwould understand that other parameters than voltage may be used, forexample, a given frequency.

Thus, after the fire command was received in step 422 and the firsttimer was started in step 424, if a voltage increase above the thresholdvoltage is not detected (second condition for firing) in step 434, theprocess returns to step 426. If the first timer has counted down thefirst time interval, as a safety measure, because the second conditionhas not been fulfilled, the process stops the timers in step 428 andreturns to the waiting step 406.

While the process loops from step 434 back to step 426 and so on duringthe first time interval, the second timer 246B counts down the secondtime interval, which is much shorter than the first time interval, whichresults in information about the status of the switch assembly beingsent in step 432 to the operator of the gun string. In this way, theoperator is constantly appraised about the status of the switchassemblies.

However, if a voltage increase above the threshold voltage is detectedby the voltage measurement unit V_(M) in step 434 while the first timeinterval has not lapsed, then the process advances to step 436 to firethe detonator 230A. Note that different from all the existing methods inthe field, the final decision to fire the detonator is made at theswitch assembly level, i.e., by the processor P_(A). In other words,while the initial decision to fire a gun assembly is made by theoperator of the gun string at the controller 206, the final decision toactually fire that gun assembly is made locally, at the switch assembly(in step 434). This split decision method ensures that the initialdecision was not a mistake and also prevents firing in error thedetonator.

As a further safety measure (a fail-safe measure), a third timer (or thefirst timer) is started in step 438 and is instructed to count down athird time interval. The third time interval may be larger than thefirst time interval, for example, in the order of minutes. In thisspecific embodiment, the third time interval is about 4 min. If thedetonator was actuated in step 436, as previously discussed, thedetonation of the charges in the gun assembly would likely destroy theswitch assembly 232A and thus the process stops here for this specificswitch assembly.

However, in the eventuality that the detonator failed to actuate, forany reason, when the processor P_(A) determines in step 440 that thethird time period has elapsed, locally decides to turn off the fireprocess in step 442 and the process returns to the waiting step 406. Theprocessor may also send a status report in step 442 to the controller206 informing that the fire process has failed. Thus, the operator maydecide to repeat the firing process or decide to skip the firing of thisgun assembly.

The processes discussed above apply to any of the switch assembliesshown in FIGS. 3A and 3B. Once the pass command has been applied to eachswitch assembly, the controller 206 is capable of instructing any of theswitch assemblies, irrespective of their position in the chain of switchassemblies, to fire its corresponding detonator, due to the selectivityafforded by the digital address. This feature is reflected in step 408,which checks for a match in the address sent by the controller 206 andthe address of each switch assembly.

Next, the process for firing the detonator of the setting tool and notthe detonator of the gun assembly associated with the lower switchassembly is discussed. If a command having the address of the lowerswitch assembly 232M is sent (see step 408 that verifies the address),and the command is valid (step 412), and the command is neither a changeaddress command (see step 414) nor a pass through command (see step418), and the command is also not a fire command (see step 422), thenthe processor P_(A) determines in step 446 whether the command isassociated with the detonator of the setting tool. If the answer is no,the process returns to the waiting step 406. If the answer is yes, theprocess advances to step 424′, which is similar to step 424 discussedabove, except that step 424′ is applicable to the setting tool detonator250 (see FIG. 2) associated with the setting tool 202.

The following steps 426′ to 442′ are similar to the corresponding steps426 to 442 and thus, their description is omitted herein. The samesafety features are implemented for the setting tool as for the gunassembly, i.e., the first to third timers. Note that actuating thedetonator of the setting tool is possible only for the lower switchassembly 232M as this switch assembly is the only one that can execute asetting tool command. This is possible because the lower switch assembly232M checks whether an indicator in the received command has a firstvalue or a second value. The first value is associated with a firecommand while the second value is associated with a setting toolcommand. Thus, when a command from the controller 206 is received andincludes the digital address of the lower switch assembly 232M and theindicator has the first value, the processor follows steps 424 to 442.However, if the command includes the digital address of the lower switchassembly 232M and the indicator has the second value, the processorfollows steps 424′ to 442′.

The setting tool associated address is set up by the controller 206 instep 414. As previously discussed, each switch assembly has a completeor partial address, either pre-assigned or randomly assigned during themanufacture process of the memory. In step 414, when the controller 206determines that the switch assembly 232M is the last one in the chain ofswitch assemblies, the controller 206 may assign an additional addressto the lower switch assembly 232M. This additional address is directlylinked to the setting tool 202 and it is checked in step 446 discussedabove.

Returning to the concept of dynamic addressing a switch assembly (seesteps 414 and 416 in FIG. 4), the following aspects are furtherdiscussed for clarification. According to this method, it is possible toset switch addresses in a gun string during the initial testing, after agun string has been assembled or at any other time. The procedure ofdynamic addressing may be accomplished using a test box or a controlsystem designed for this purpose, for example, the controller 206.

In one application, upon power being applied to the chain of switchassemblies, the first switch assembly powers up, performs internaltesting of its circuits, and tests for the presence of a detonator.After a short delay, it sends up this information (see step 402) to thetest box with an uninitialized address. The test box will recognize thisaddress and sends a command (see step 414) which instructs the switchassembly to reprogram its address to the one sent in the command. Thetest box then sends the “pass through” command in step 418. At thispoint, the switch assembly will “pass through” the voltage to the nextswitch assembly in the chain, and the process is repeated until all theswitch assemblies in the chain are accounted for.

During the operation of the gun string, the surface logging and/orperforating system (i.e., controller 206) may poll the gun string. Thispolling process is initiated by applying power to the upper switchassembly 232A in the gun string. Upon powering up, the upper switchassembly transmits its address up the wireline and then automaticallyreverts to a low power listening mode state. The controller 206 receivesand identifies the unique address of the switch assembly and positionsthis switch assembly in the gun string. Then, the controller 206transmits a digital code (pass through command) back down-hole to theswitch assembly that instructs the switch assembly to apply power to thenext switch assembly in the string below.

Power is then applied to the next switch assembly down the gun string.The process is repeated for each switch assembly or any number of gunassemblies in a gun string. When the controller 206 detects the lowerswitch assembly in the string, a record of the number, address andposition in the gun string of all the switch assemblies is recorded.

The switch assemblies have been designed with a dual purpose feature.The switch assembly can be set for (1) a normal mode fire with passthrough, or (2) a setting tool mode fire. The setting tool mode can beused for a setting tool and the associated lower gun assembly. A uniqueaddress may be used to determine which mode to be used. The setting toolmode will follow the same fire procedure to set a plug as discussedabove with regard to FIG. 4.

After all the switch assemblies in a gun string are powered up and allthe addresses are recorded, all the switch assemblies in the gun stringare in the “wait for command,” low power consumption mode. The operatormay then select any switch assembly in the gun string and send a “FireCommand.” Note that the operator does not have to start with the lowergun assembly. With the addressable switch assemblies discussed herein,the operator has the freedom to actuate any switch assembly, whereverpositioned in the chain of the switch assemblies. The unique digitaladdress code for a specific switch assembly in the gun string istransmitted immediately followed by a unique digital coded fire command.Once the correctly addressed switch assembly understands its addresscode, the command initiates an internal timer (see step 424). Insidethis timer loop, the switch assembly sends up the wireline astatus/reset code (see step 432) at 1 second interval giving theoperator a visual indication of the ready to fire state of the switchassembly. This timer loop is user programmable from 10 to 60 seconds andindicates the time remaining before the switch assembly will abort thefire command and revert back to normal operation in its previouslyconfigured state. Note that the time interval with which the one or moretimers are programmed in the switch assembly may be programmed beforethe switch assemblies are lowered into the well, but also after they areplaced inside the well (see step 414).

The switch assembly's internal voltage measurement circuits monitors thethru-line voltage. If the line voltage is increased above the thresholdvoltage (e.g., 140 Volts) before the first timer times out, the voltageis applied to the detonator that is hard wired to the switch assembly byclosing the detonator switch. If the voltage is not increased within thetime allotted by the first timer, the fire command is aborted and mustbe re-sent from the surface system to start another time out window.Once the voltage is above the threshold voltage and the line has beenconnected to the detonator, another timer (third timer, see step 438) isstarted. In one application, this timer is about 4 minutes and ensuresthat the detonator is disconnected from the line in case the detonatordoes not fire for any reason.

The previous embodiments discussed how various commands are sent fromthe controller 206 to the switch assemblies and how the switchassemblies send various information (e.g., their digital addresses ortheir status) to the controller. Thus, a bi-directional communication isestablished between the controller and the switch assemblies. Onepossible implementation of the various commands that are exchangedbetween the controller and the switch assemblies are now discussed.

According to an embodiment, communications between the controller 206and the addressable switch assemblies is based on a frequency-shiftkeying (FSK) communication scheme. Binary data is encoded into the FSKscheme and the data is driven over the wireline (the thru-line), whereeach bit is represented by, for example, 1.5 ms of pulses. In oneapplication, a zero is represented by 4 cycles of 2.666 kHz and a one isrepresented by 6 cycles of 4 kHz. These are exemplary numbers and thoseskilled in the art would understand that other numbers may be used.Others modulation schemes may be used for the communications between thecontroller and the switch assemblies.

In one application, upon the initial power-up of a switch assembly, theswitch assembly sends a 10-byte uplink to the surface controller toidentify itself and also may send certain status information. Thesurface controller can then send a 10-byte downlink to the switchassembly with various commands, as outlined below. For both the uplinkand downlink, the format of a frame 500 used to carry the commands maybe as illustrated in FIG. 5.

The first command in a transmitted packet is LEN 502. This command willalways read 0x09, as the payload length is 9 bytes. The second commandis ADDY 504. This command has three bytes, and together they constitutethe 24-bit address of the individual switch. This third command is CMD506. This command is a two-byte command issued to a given switchassembly. The actions associated with the two bytes is discussed later,but may include the above discussed commands, e.g., fire, pass-thou,set. The fourth command is INT 508. This command can be used to passswitch data to the surface, for instance, to convey an (analog todigital) ADC reading of the voltage. The fifth command is STAT 510. Thiscommand is a status byte that can convey certain data via bit-flags,e.g., 1—the switch assembly function correctly, 2—the detonator gun isopen, 3—the thru-line switch is open, etc. The sixth command is CKSUM512. This command is the sum (truncated to 8-bits) of all previous bytesin the packet.

When a switch assembly is first powered, in one embodiment, a standardconfiguration switch assembly may send two identical uplink packets witha given (e.g., 50 ms) time gap between packets. The packet will be inthe format illustrated in FIG. 5, with the INT field containing thefirmware version number and the STAT field representing the status ofthe resistor dividers sensing the Fire and Feedthrough lines. Bits 6 and7 of STAT represent the voltage levels on the Feedthrough and Firevoltages respectively. If a detonator is detected on the fire line, Bit7 will be set. If termination is detected on the Feedthrough line, Bit 6will be set.

Several of the commands to be discussed next will result in an ADC valuebeing sent to surface in the INT field. To convert these values to anactual voltage, note that the ADC (which is part of the voltage moduleV_(M) in FIG. 3A) has 4 mV/LSB (where LSB is the least significant bit)resolution and the ADC inputs are coming through a resistor divider(e.g., a/151 resistor divider). Therefore, if an ADC reading of 19 isreceived, the actual measured voltage is 19*(4 mV*151)=11.5 V.

In one embodiment, the commands 506 that can be sent by the controllerto the switch assemblies are as follow:

(1) Pass-Through command has values in the range of 0x13 to 0xE5. Thiscommand enables the bypass line 204-o of a switch assembly (i.e., closesthe thru-line switch 234);

(2) Fire command has values in the range of 0xEC to 0x64. This commandenables the fire line 236A/B (i.e., closes the detonator switch 230).After sending the Fire command, the line voltage must be raised abovethe threshold voltage within a specific time window (default time is thefirst time interval in seconds), at which point this increased voltagewill be dumped onto the fire line.

(3) New Address command has values in the range of 0x0D to 0x80. Thiscommand is used by the controller to set a switch assembly with a newaddress. The controller sends a downlink of the New Address command,with the new address in the INT and STAT positions, which will reprogramthe switch assembly's address.

(4) Un-bypass command has values in the range of 0x5D to 0xA6. Thiscommand is used by the surface controller to turn of a bypass line,i.e., if a thru-line switch 234 has previously been bypassed with thePass-Through command, this command will turn off the bypass line, i.e.,will open the switch 234.

(5) Set Fire command has values in the range of 0x15 to 0x63. Thiscommand initiate the activation of the setting tool detonator. If theswitch assembly has an address in the Setting Switch range, this commandwill enable the Fire line in order to activate the setting tool. TheVoltage/window are as described above for the FIRE command.

(6) Vrail Sense command has values in the range of 0xDD to 0x65. Thiscommand reports the voltage on the thru-line with scaling as notedabove.

(7) Set Sense command has values in the range of 0x41 to 0x53. In thecase of a bottom switch assembly (that also serves a setting tool), thiscommand reports the voltage on the Set/Fire line.

(8) Fire Sense command has values in the range of 0xD2 to 0xC2. In thecase of a standard switch assembly, this command reports the voltage onthe Fire line.

(9) FW revision command has values in the range of 0x19 to 0xEB. Thiscommand reports the current firmware revision in the INT field.

(10) Fire Time command has values in the range of 0x32 to 0x79. Thiscommand dictates the time window between sending the Fire command andwhen the voltage must pass the threshold voltage in order to activatethe Fire line. The new time must be in a given range (e.g., 10-60seconds) and will be sent in the STAT field.

The protocol described in this embodiment is applicable to switchassemblies used in a wireless router (WRT), a lower switch assembly(that is also connected to a setting tool) and a standard switchassembly (not connected to a setting tool). Any particular switchassembly will have an address that corresponds to itsconfiguration/roll. In one application, the address ranges for the abovenoted switch assemblies may be as follows:

WRT Address Range: 0xFFFD00-0xFFFFFE,

lower switch assembly Address Range: 0xFFFC00-0xFFFCFF, and

standard switch assembly Address Range: 0x000000-0xFFFFBF.

The physical location of a switch assembly 232 has been assumed in FIG.2 to be inside a sub that is associated with a gun assembly. However, itis possible to place the switch assembly at other locations along thegun string as now discussed. For example, according to an embodimentillustrated in FIG. 6, a system 600 includes a gun string 601 located ina wellbore 211. The controller 206 is located at the surface, next tothe head of the wellbore 211. The thru-line 210 extends from thecontroller 206 to the gun string 601. The thru-line 210 may be part of awireline. The gun string 601 includes plural subs (only two subs 610 and620 are shown) and plural gun assemblies (only one 630 is shown)connected to each other. The last gun assembly is connected to a settingtool 202. A setting tool detonator 250 may be located either in thesetting tool 202 or in an adjacent sub, gun assembly or setting toolkit. When located in the well, the first sub 610 is upstream from thegun assembly 630 and the second sub 620 is downstream.

While the traditional gun strings have each gun assembly directlysandwiched between two adjacent subs, according to this embodiment,there is an additional element, a detonator block 640 located betweenthe first sub 610 and the gun assembly 630 and also a contact end platemechanism 632 that ensures electrical connection between the detonatorblock 640 and the gun assembly 630. This electrical connection does notinvolve wires, as discussed later. A switch assembly 232 and a detonator642 are located inside the detonator block 640. Contact end platemechanism 632 also connects to a detonation cord 634 that actuates thecharges 638 in the gun assembly 630. FIG. 6 shows the detonation cord634 being located outside a charge load tube 636. The charge load tube636 is configured to hold the various charges 638. FIG. 6 also shows acarrier 639 connected to the sub 610 and housing the components of thegun assembly. Each gun assembly of the gun string may be connected to acorresponding detonator block 640, that holds a corresponding switchassembly 232 and detonator 642.

Thus, according to this embodiment, neither the detonator 642 nor theswitch assembly 232 are located in the sub 610 or 620 as in thetraditional gun strings. This is advantageous because the repeatedactivation of the detonator slowly damages the sub, which is expensiveto replace. However, the cost of the detonator block 640 is lower thanthe cost of the sub as the detonator block may be made of cheapermaterials (e.g., polymers) and thus it can be changed more often.Details of the detonator block 640 and contact end plate mechanism 632are now discussed.

FIG. 7 shows a half of the detonator block 640 having the detonator 642installed in a chamber 645 formed in a body 641 of the detonator block.Detonator 642 may be held in place by one or more holders 643 (e.g.,off-the-self fuse holders). This means that any type of detonator may beplaced inside the detonator block 640. A first end 644A of the body 641is narrower than the rest of the body and has corresponding threads 646that are designed to mate with corresponding threads in the sub 610.Note that a traditional sub 610 has a switch retainer nut that holds inplace the corresponding switch. The present detonator block 640 isconfigured to replace the switch retainer nut in the sub 610. This meansthat detonator block 640 screws directly into the body of the first sub610 when the gun string is assembled. However, only the first end 644Aof the detonator block enters inside the sub, which means that theswitch assembly 232 remains outside the sub.

The second end 644B of the detonator block 640 has a more complexstructure. Plural spring-loaded contacts 646A to 646C (more or lesscontacts may be used in another embodiment) are attached to a printedcircuit board (PCB) 648 and located so that corresponding pins 647A to647C extend beyond the body 641. The PCB 648 is placed inside thedetonator block. In one embodiment, the PCB 648 extends around thedetonator 642 as shown in FIG. 7. The three spring-loaded contacts 647Ato 646C connect to the thru-line, fire-line and dedicated ground line,respectively. As will be discussed later, these three electricalcontacts connect to corresponding contacts on the contact end platemechanism 632 discussed with regard to FIG. 6. These connectors arespring loaded to account for any variations in assembly which mightotherwise prevent one of the connectors from making contact with acorresponding contact on the contact end plate mechanism.

On the same PCB 648 is located the switch assembly 232 and optionally, acontact switch 650. The switch assembly 232 has been discussed aboveextensively and its configuration is omitted herein. The contact switch650 shunts the leads of the detonator 642 when the assembly is notcompleted. This is a safety feature which prevents an unwanteddetonation of the detonator, in addition to the safety featuresdiscussed above with regard to the switch assembly 232. Note that thedetonator cannot be electrically actuated as long as its leads areconnected to each other. In this regard, detonator 642 has two leads642A and 642B that are connected to a wire header 654, which is attachedto the PCB 648. The two leads 642A and 642B are shorted by the contactswitch 650 when a head 652 of this switch is free, i.e., not in contactwith anything. As soon as head 652, which can be made of plastic, isbiased by the contact end plate mechanism 632, the two leads 642A and642B are electrically disconnected from each other. However, these leadsremain connected to the rest of the circuit. Contact switch 650 may be anormally closed, momentary contact switch.

The PCB 648 electrically connects the ground contact 646A to acorresponding ground pin 646A-A and the thru-line contact 646B to theswitch assembly 232. The switch assembly 232 is also connected to acorresponding thru-line pin 246B-B. The switch contact 646C may beelectrically connected to a corresponding switch assembly in adownstream detonator block and also to the wire header 654 and to thecontact switch 650. Pins 646A-A and 646B-B ensure that the ground-line(if present) and the thru-line continue to the next gun assembly, asillustrated in FIG. 2.

The detonator block may further include another safety feature, theinterrupter mechanism 660. The interrupter mechanism 660 includes, amongother elements, a cap 662 and an arm 664. Cap 662 is placed to block aballistic connection between the detonator 642 and the detonation cord634 of the gun assembly 630. This means that even if the detonator 642is accidentally actuated, the produced pressure waves would not ignitethe detonation cord 634 inside the gun 630, and thus, the explosivecharges 638 of the gun assembly would not be actuated. Cap 662 may havethe same or a larger diameter than the detonator 642 for preventing thepressure waves from the detonator to propagate downstream to the gun630. Note that the detonator block does not have to simultaneously haveall the safety features discussed herein. In one embodiment, only thesafety features provided by the addressable switch assembly 232 arepresent. The detonator block may include any one or more of theseadditional safety features. In one application, the detonator block mayinclude any combination of these safety features.

The configuration of the contact end plate mechanism 632 is nowdiscussed with regard to FIGS. 8 and 9. Note that the contact end platemechanism 632 may take the place of a conventional upstream endplate fora gun assembly. FIG. 8 shows a front face 800 of the contact end platemechanism 632 and this front face electrically and mechanically connectsto the detonator block 640. For achieving the electrical connection withthe detonator block, the front face includes a printed circuit board 801that has three electrical contacts (other number may be used in otherapplications) 802, 804, and 806, which are electrically separated fromeach other by insulating zones 808. The electrical contacts 802, 804,and 806 may be formed as rings on the printed circuit board. In oneapplication, these electrical contacts may have another shape.

One skilled in the art would appreciate at least two advantages of theseelectrical contacts. First, the process of making these contacts (i.e.,treating a printed circuit board to have three concentric rings) iseasier and cheaper than stamping metal contacts as currently done in theindustry. Second, the current guns require an accurate alignment of thevarious components for matching the electrical contacts of these variouscomponents. In the present embodiments, the three electrical contacts646A, 646B, and 646C of the detonator block 640 and the correspondingthree electrical contacts 802, 804, and 806 of the contact end platemechanism 632 do not need to exactly match each other because of thecircular shape of the contacts 802, 804, and 806. In other words, theelectrical contacts of the detonator block may be rotated in any wayrelative to their longitudinal axis X and they still contact theelectrical contacts of the contact end plate mechanism. Further, even ifthere is a gap between the detonator block and the contact end platemechanism along the axis X, because of the springs biasing the pins ofthe electrical contacts of the detonator block against the contact endplate mechanism, a good electrical contact is achieved between thedetonator block and the contact end plate mechanism. Thus, assembly ofthe detonator block and the contact end plate mechanism is simplified asno precise alignment of the two parts is required.

In one embodiment, the detonator block 640 connects to a gun 630 as nowdiscussed. The downhole tool 601 shown in FIG. 6 includes a first gunassembly element (e.g., gun 630) having a contact end plate mechanism632 and a second gun assembly element (e.g., detonator block 640) havingtwo or more spring-loaded contacts 646A, 646B. The two or morespring-loaded contacts 646A, 646B of the second gun assembly element 640make an electrical contact with to the two or more round electricalcontacts 802, 804. In this embodiment, the two or more spring-loadedcontacts 646A, 646B maintain the electrical contact with the two or moreround electrical contacts 802, 804 while the two or more spring-loadedcontacts rotate about a longitudinal axis of the downhole tool.

The contact end plate mechanism 832 shown in FIG. 8 also has a centralhole 810, through which the pressure waves from the detonatorballistically communicate with the detonator cord that is attachedbehind the PCB front face 800 (see FIG. 9). FIG. 8 also shows a bracket812 that maintains the PCB front face 800 attached to the contact endplate mechanism 632. This feature is better seen in FIG. 9. This figureshows the body 820 of the contact end plate mechanism 632, the PCB frontface 800 being in contact with the body 820, and the bracket (orretainer) 812 clipping the PCB front face 800 to the body 820.Optionally, a spring 822 may be placed between the body 820 and the backof the PCB front face 800 to bias it against the detonator block.

FIG. 9 also shows a cord holder 826 that enters through the central hole810 of the PCB front face 800 and attaches to the body 820 of thecontact end plate mechanism 832, for example, with clamps 828. Thedetonation cord 634 is shown having a bidirectional booster 830 and boththe detonation cord and the bidirectional booster attach to an insidethe cord holder 826. In this way, the detonation cord is centeredrelative to the PCB front face and also aligned with the opening 810 sothat the pressure waves from the detonator can ignite the bidirectionalbooster. The bidirectional booster is a more sensitive element formaking sure that the pressure waves from the detonator ignite thedetonation cord. However, the bidirectional booster is not required andthere are guns that do not use such boosters.

On the back of the PCB front face 800, an electrical connector 840 maybe attached and this connector electrically connects the threeelectrical contacts 802, 804, and 806 to corresponding wires 802′, 804′and 806′ for extending the ground, thru-line and fire-line along the gunassembly 630. FIG. 9 shows the gun assembly 630 having the contact endplate mechanism 632 attached to the charge load tube 636. The chargeload tube is used to hold the charges 638 that are detonated in the wellfor connecting the formation to the interior of the well. The detonationcord 634 actuates these charges and this cord is shown in FIG. 6 beinglocated around the charge load tube 636.

To attach the contact end plate mechanism 632 to the charge load tube636, one or more clamps 842 may be used. In one application, the one ormore clamps 842 may be formed in the body 820 of the contact end platemechanism 632, as shown in FIG. 9. However, those skilled in the artwould understand that other methods and means for attaching the contactend plate mechanism to the charge load tube may be used (e.g., using atwist-lok type of interface). In one application, for example, threadsmay be formed in the body 820 of the contact end plate mechanism and thecharge load tube and the contact end plate mechanism may be screwed tothe charge load tube. The clamps shown in FIG. 9 are more advantageousbecause no twist of the internal wires is produced and also using clampsis cheaper and faster than screwing the contact end plate mechanism.

FIG. 10 shows the detonator block 640 mechanically attached to the firstsub 610 and the detonator block 640 also in electrical and mechanicalcontact with the contact end plate mechanism 632. Note that in anotherembodiment, first sub 610 can be replaced with another gun assembly. Inthis embodiment, the detonator block 640 includes a switch assembly 232and the detonator block is connected between first gun 610 and secondgun 630. Those skilled in the art would understand that the switchassembly may be located in the sub 610 instead of the detonator block640 and only the detonator may be located inside the detonator block.Reference sign 610 indicates in this figure a gun assembly element,which can be a sub, a gun, or other component of the gun assembly. Thecontact end plate mechanism 632 is already attached to the charge loadtube 636 of the gun assembly 630. When the detonator block 640 ismechanically and electrically attached to the contact end platemechanism 632, as in FIG. 10, the contact switch 650 (if present)touches the contact end plate mechanism, which de-shunts the leads ofthe detonator 642. In addition, the mechanical contact (if present)between the detonator block and the contact end plate mechanism pushesthe interrupter actuator along the axis X, which results in the cap 662clearing the path between the detonator 642 and the detonator cord 634,i.e., achieving a ballistic communication. Further, when the detonatorblock 640 is in mechanical contact with the contact end plate mechanism632, the spring-loaded contacts 646A, 646B, and 646C electricallyconnect to the contacts 802, 804, and 806 of the contact end platemechanism 832. Thus, the switch assembly 232 electrically connects toother switch assemblies through circuit board contacts.

As discussed above with regard to FIG. 9, the contact end platemechanism 632 connects to the charge load tube 636 via snap tabs 842,which are also shown in FIG. 10. The contact end plate mechanism 632 canbe made from a variety of materials and with plural manufacturingmethods (e.g., injection molding plastic). The contact end platemechanism 632 and the change load tube 636 are located inside thecarrier 639. Carrier 639 connects to the sub 610 by mating threads 639Aand 610A at a first end of the carrier. The carrier 639 connects to thesecond sub 620 (shown in FIG. 6) with corresponding mating threads (notshown) similar to the threads 639A and 610A. Carrier 639 protects theother components of the gun assembly 630 from the fluid present insidethe well. Note that the detonation block is screwed to the sub andlocated outside the sub. Also, in this embodiment, the detonation blockis located inside the carrier 639, but outside the change load tube 636.

While the various features illustrated above have been discussed in thecontext of the oil and gas industry, those skilled in the art wouldunderstand that the novel features are applicable to devices in anyfield. For example, the rotatable multipin connection between thedetonator block and the contact end plate mechanism utilizing theprinted circuit board as an electromechanical connection may be used inthe electronics field. The spring loading of the pins 647A to 647C mayaccount for tolerances in makeup and add practicality to any twoelements that need to be electrically connected. Furthermore, the costof such PCB connector is much below other multipin designs.

The various embodiments discussed above may be implemented as nowdiscussed. According to an embodiment illustrated in FIG. 11, there is amethod for controlling a target switch assembly 232A in a chain ofswitch assemblies 232A to 232M (see FIG. 2). The method includes a step1100 of distributing the chain of switch assemblies in a wellbore 211, astep 1102 of placing a controller at a head of the wellbore, a step 1104of making a first decision, at the controller, to actuate acorresponding detonator of the target switch assembly, a step 1106 oftransmitting, from the controller to the target switch assembly, a firecommand to activate the corresponding detonator, and a step 1108 ofmaking a second decision, locally, at the target switch assembly, toactivate the detonator, after the fire command from the controller isreceived.

In this method, each switch assembly of the chain of switch assemblieshas a unique digital address. In one application, each switch assemblyof the chain of switch assemblies includes a detonator switch and athru-line switch. In another application, the detonator switch activatesthe corresponding detonator and the thru-line switch allows a voltage ina thru-line to pass from the target switch assembly to an adjacentswitch assembly. The thru-line extends from the controller to the targetswitch assembly and the fire command is transmitted along the thru-line.

The method may further include a step of measuring a voltage, at thetarget switch assembly, of a thru-line that extends from the controllerto the target switch assembly. When the measured voltage is larger thana threshold voltage, according to this method, the switch assemblyactuates the corresponding detonator. The method may also includestarting a first timer upon receiving the fire command, where the firsttimer counts a given first time period. Further, the method may includea step of measuring a voltage, at the target switch assembly, of athru-line that extends from the controller to the target switchassembly, and when the measured voltage is larger than a thresholdvoltage, and when the first time period has not lapsed, actuating thecorresponding detonator.

The method may also start a second timer when the detonator is actuated.In this case, the method switches off a detonator switch when a secondtime period of the second timer has elapsed.

Alternatively, the method may include a step of measuring a voltage, atthe switch assembly, of a thru-line that extends from the controller tothe target switch assembly, and when the measured voltage is larger thana threshold voltage, but the first time period has lapsed, not actuatingthe corresponding detonator. Another alternative for the method is tomeasure a voltage, at the target switch assembly, of a thru-line thatextends from the controller to the target switch assembly, and, when themeasured voltage is not larger than a threshold voltage, to not actuatethe corresponding detonator.

According to another variation, the method may start a second timer uponreceiving the fire command, where the second timer counts a given secondtime period, which is shorter than the first time period. According tothis variation, the method may include a step of sending statusinformation from the target switch assembly to the controller when thesecond time period has elapsed.

According to another embodiment, the method may include a step ofinserting into the fire command, at the controller, a digital address ofthe target switch assembly.

A switch assembly 232A that may implement the above method is nowdiscussed. The switch assembly, which is part of a chain of switchassemblies 232A to 232M, includes a communication unit (CU) that isconfigured to receive, from an external controller 206, a fire commandto activate a detonator 230A; and a computing core (CC) configured tolocally make a decision to activate the detonator 230A, based on (i) ameasured parameter (V), (ii) a threshold value of the measured parameter(V), and (iii) the fire command.

The switch assembly may also include a detonator switch electricallyconnected to the detonator, a thru-line switch connected to a thru-linethat extends to the external controller, a voltage measurement unit formeasuring the parameter, where the parameter is a voltage of thethru-line, and a permanent memory that stores a unique digital address.

In one embodiment, the switch assembly may also include a first timerwhich is started upon receiving the fire command, where the first timercounts a given first time period. The switch assembly may also include asecond timer which is also started upon receiving the fire command,where the second timer counts a given second time period, which isshorter than the given first time period.

The method discussed above with regard to FIG. 11 may be implemented ina downhole system 600 (as illustrated in FIG. 6). Such a system mayinclude a controller 206 located at the surface; a gun string 601located in a wellbore 211, the gun string 601 including plural gunassemblies 630; a thru-line 210 connecting the controller 206 to the gunstring 601; and a detonator block 640 attached to a given gun assembly630. The detonator block 640 includes an addressable switch assembly232.

This system may further include a detonator 642 electrically connectedto the switch assembly 232. The detonator may be located inside thedetonator block. The system may also include a sub connected to an endof the detonator block, which is opposite to the gun assembly. The gunassembly includes an end plate mechanism 632 that electrically connectsto the detonator block.

In one application, the detonator block has at least one spring-loadedcontact connected to the thru-line and the end plate mechanism 632includes a round electrical contact 806 made as a printed circuit board,and the spring-loaded contact touches the printed circuit board. In oneapplication, the printed circuit board is circular.

According to another embodiment, there is a method, as illustrated inFIG. 12, for selectively firing a setting tool detonator 250 and a gunassembly detonator 230M. The method includes a step 1200 of connectingan addressable switch assembly 232M to the setting tool detonator 250and to the gun assembly detonator, a step 1202 of placing theaddressable switch assembly 232M, the setting tool detonator 250, andthe gun assembly detonator 230M inside a wellbore, a step 1204 ofreceiving a command at the addressable switch assembly, from a surfacecontroller 206, wherein the command includes a digital address and anindicator, and a step 1206 of firing the gun assembly detonator 230M ifthe indicator has a first value and firing the setting tool detonator250 if the indicator has a second value, different from the first value.

The indicator takes only the first or second values. In one application,the switch assembly decides locally to activate the setting tooldetonator 250, after receiving the command. In another application, theswitch assembly decides locally to activate the gun assembly detonator230M, after receiving the command. The first value is fire and thesecond value is set.

The method may further include a step of measuring a voltage, at theswitch assembly, of a thru-line that extends from the controller to theswitch assembly. In one application, the method includes, when themeasured voltage is larger than a threshold voltage and the indicatorhas the first value, actuating the gun assembly detonator.Alternatively, the method may include, when the measured voltage islarger than a threshold voltage and the indicator has the second value,actuating the setting tool detonator. In one application, the methodstarts a first timer upon receiving the command, where the first timercounts a given first time period.

The method may further include a step of measuring a voltage, at theswitch assembly, of a thru-line that extends from the controller to theswitch assembly; and, when the measured voltage is larger than athreshold voltage, the first time period has not lapsed, and theindicator has the first value, actuating the gun assembly detonator.

In one application, the method measures a voltage, at the switchassembly, of a thru-line that extends from the controller to the switchassembly; and when the measured voltage is larger than a thresholdvoltage, the first time period has not lapsed, and the indicator has thesecond value, actuating the setting tool detonator. In one embodiment,the method starts a second timer when the gun assembly detonator or thesetting tool detonator is actuated.

The method may also include a step of switching off a detonator switchwhen a second time period of the second timer has elapsed, and/orstarting a second timer upon receiving the command, wherein the secondtimer counts a given second time period, which is shorter than the firsttime period. In still another application, the method may include a stepof sending status information from the switch assembly to the controllerwhen the second time period has elapsed.

The method discussed above with regard to FIG. 12 may be implemented ina switch assembly 232M, which is part of a chain of switch assemblies232A to 232M. The switch assembly includes a communication unit (CU)configured to receive, from an external controller 206, a command toactivate a gun assembly detonator 230M or a setting tool detonator 250,and a computing core (CC) configured to locally make a decision toactivate one of the gun assembly detonator 230M or the setting tooldetonator 250, based on (i) a measured parameter (V), (ii) a thresholdvalue of the measured parameter (V), and (iii) the received command.

The switch assembly may also include a first switch electricallyconnected to the gun assembly detonator; and a second switchelectrically connected to the setting tool detonator. The switchassembly may further include a thru-line switch connected to a thru-linethat extends to the external controller, and a voltage measurement unitfor measuring the parameter. The parameter is a voltage of thethru-line. The switch assembly may further include a permanent memorythat stores a unique digital address, and a first timer which is startedupon receiving the command. The first timer counts a given first timeperiod. If the switch assembly includes a second timer, which is alsostarted upon receiving the command, the second timer counts a givensecond time period, which is shorter than the given first time period.

The method discussed above may also be implemented in a downhole system600 as illustrated in FIG. 6. The downhole includes a controller 206located at the surface; a gun string 601 located in a wellbore 211, thegun string 601 including plural gun assemblies 630 and a setting tool202, a thru-line 210 connecting the controller 206 to the gun string601, and at least an addressable switch assembly 232 configured toactuate a gun assembly detonator 642 and a setting tool detonator 250.The system may further include a detonator block 640 located adjacent toa gun assembly 630, where both the addressable switch assembly and thegun assembly detonator are located inside the detonator block. In oneapplication, the system includes a sub connected to an end of thedetonator block, which is opposite to the gun assembly. The gun assemblyincludes an end plate mechanism 632 that electrically connects to thedetonator block. In this application, the detonator block has at leastone spring-loaded contact connected to the thru-line and the end platemechanism 632 includes a round electrical contact 806 made as a printedcircuit board, and the spring-loaded contact touches the printed circuitboard.

The disclosed embodiments provide methods and systems for selectivelyactuating one or more gun assemblies in a gun string. It should beunderstood that this description is not intended to limit the invention.On the contrary, the exemplary embodiments are intended to coveralternatives, modifications and equivalents, which are included in thespirit and scope of the invention as defined by the appended claims.Further, in the detailed description of the exemplary embodiments,numerous specific details are set forth in order to provide acomprehensive understanding of the claimed invention. However, oneskilled in the art would understand that various embodiments may bepracticed without such specific details.

Although the features and elements of the present exemplary embodimentsare described in the embodiments in particular combinations, eachfeature or element can be used alone without the other features andelements of the embodiments or in various combinations with or withoutother features and elements disclosed herein.

This written description uses examples of the subject matter disclosedto enable any person skilled in the art to practice the same, includingmaking and using any devices or systems and performing any incorporatedmethods. The patentable scope of the subject matter is defined by theclaims, and may include other examples that occur to those skilled inthe art. Such other examples are intended to be within the scope of theclaims.

What is claimed is:
 1. A method for controlling a target switch assemblyin a chain of switch assemblies, the method comprising: distributing thechain of switch assemblies in a wellbore; placing a controller at a headof the wellbore; making a first decision, at the controller, to actuatea corresponding detonator of the target switch assembly; transmitting,from the controller to the target switch assembly, a fire command toactivate the corresponding detonator; and making a second decision,locally, at the target switch assembly, whether or not to activate thedetonator, after the fire command from the controller is received, basedon whether or not a voltage measured by the target switch assembly atthe target switch assembly is larger than a threshold voltage.
 2. Themethod of claim 1, wherein each switch assembly of the chain of switchassemblies has a unique digital address.
 3. The method of claim 1,wherein each switch assembly of the chain of switch assemblies includesa detonator switch and a thru-line switch.
 4. The method of claim 3,wherein the detonator switch activates the corresponding detonator andthe thru-line switch allows a voltage in a thru-line to pass from thetarget switch assembly to an adjacent switch assembly.
 5. The method ofclaim 1, wherein a thru-line extends from the controller to the targetswitch assembly and the fire command is transmitted along the thru-line.6. The method of claim 1, further comprising: measuring the voltage, atthe target switch assembly, of a thru-line that extends from thecontroller to the target switch assembly.
 7. The method of claim 6,further comprising: when the measured voltage is larger than thethreshold voltage, actuating the corresponding detonator.
 8. The methodof claim 1, further comprising: starting a first timer upon receivingthe fire command, wherein the first timer counts a given first timeperiod.
 9. The method of claim 8, further comprising: measuring thevoltage, at the target switch assembly, of a thru-line that extends fromthe controller to the target switch assembly; and when the measuredvoltage is larger than the threshold voltage, and when the first timeperiod has not lapsed, actuating the corresponding detonator.
 10. Themethod of claim 9, further comprising: starting a second timer when thedetonator is actuated.
 11. The method of claim 10, further comprising:switching off a detonator switch when a second time period of the secondtimer has elapsed.
 12. The method of claim 8, further comprising:measuring the voltage, at the switch assembly, of a thru-line thatextends from the controller to the target switch assembly; and when themeasured voltage is larger than the threshold voltage, but the firsttime period has lapsed, not actuating the corresponding detonator. 13.The method of claim 8, further comprising: measuring the voltage, at thetarget switch assembly, of a thru-line that extends from the controllerto the target switch assembly; and when the measured voltage is notlarger than the threshold voltage, not actuating the correspondingdetonator.
 14. The method of claim 8, further comprising: starting asecond timer upon receiving the fire command, wherein the second timercounts a given second time period, which is shorter than the first timeperiod.
 15. The method of claim 14, further comprising: sending statusinformation from the target switch assembly to the controller when thesecond time period has elapsed.
 16. The method of claim 1, furthercomprising: inserting into the fire command, at the controller, adigital address of the target switch assembly.